The present invention relates to means for driving a vehicle, such as a rider-type lawnmower or a small tractor, wherein the output shaft of an engine is interconnected by a belt drive to a transaxle or transmission which, in turn, is joined to the drive wheels of the vehicle.
The operation of a vehicle of the foregoing type normally requires several speeds in order to accomplish various functions for which the vehicle has been designed. To provide multispeed operation, a gear set conventionally is provided in a gear box. The gear relationships for different speeds then are selected by the operator. However, such an arrangement often is inadequate. For example, due to the differences between gear relationships, it is not infrequently the case that for a particular operation, a given gear selection may cause the engine to stall under load, while the next lowest gear selection may hardly load the engine at all. It therefore is desirable that a variable speed drive be provided to accommodate the differing load requirements likely to be encountered by a rider-type lawnmower or small tractor.
In U.S. Pat. No. 4,310,082 which issued on Jan. 12, 1982 to Raymond L. Elmy, et al, and which is assigned to the assignee of the present application, there is disclosed a belt drive arrangement incorporating a variator which interconnects an engine and the wheel drive of a ground-engaging vehicle. Such a drive arrangement provides a variable speed changing device between the engine and the wheel drive which can be altered without adjusting the engine's throttle and without stopping the vehicle to change gears.
The present invention constitutes an improvement over the variator arrangement disclosed in U.S. Pat. No. 4,310,082. More particularly, the previously patented structure requires a complex linkage to achieve primary and secondary braking functions. The control of the variator by a clutch/brake pedal also requires a camming arrangement and a multiple spring biasing system.